188 ANAUCHEN. 



The texture, sculpture and form show that this species be- 

 longs to the luzonicum group, or at least that it was derived 

 from some form of that group ; but it has diverged remark- 

 ably in a single character, the loss of all teeth. Two specimens 

 measure : 



Alt. 2.6, greatest diameter 3.25 mm. 



Alt. 2.75, greatest diameter 3.2 mm. 



Genus ANAUCHEN, n. gen. 



The shell is umbilicate, pyramidal, light-colored and spirally 

 striate, last whorl scarcely or not ascending and not free. 

 The aperture is rounded, oblique, the peristome broadly ex- 

 panded but thin, shortly adnate above. No angular lamella; 

 parietal and columellar lamellae developed, the latter hori- 

 zontal ; 0-3 plicse in the lip. 



Typejff. gereti (B. &D.). 



This group is peculiar for having lost the angular lamella, 

 leaving a simple parietal. Except in H. messageri, the other 

 teeth are more or less completely degenerate. I do not know 

 whether A. rochebruni and angulina are spirally striate or 

 not. All but the last are from Tonkin. 



This group is related to Hypselostoma by the spiral sculp- 

 ture but differs by having no angular lamella, and the last 

 whorl is adnate. This last is not a very important difference, 

 and one which may perhaps disappear with future discoveries. 

 I do not think it closely related to Boysidia. 



Key to Species. 



a. Last whorl swollen but not angular. 



b. Five well-developed teeth; alt. 3, diam. 2.5 mm. or 



smaller. A. messageri, no. 1. 



ft 1 . Three small teeth, parietal, columellar and lower 



palatal ; alt. 3.5, diam. 2.7 mm. A. gereti, no. 2. 



a 1 . Last whorl somewhat angular at periphery and umbilicus. 



6. Two teeth, parietal and lower palatal ; alt. 4, diam. 



3 mm. A. rochebruni, no. 3. 



& 1 . A parietal tooth only; alt. 3%, diam. 2% mm. 



A. angulinus, no. 4. 



